There are several ways to fabricate magneto-resistive (MR) sensors for read back of data on magnetic tape. In all cases, a bias method must be used in order to permit the sensor to operate in the linear portion of the MR curve. In some cases, two elements can be used at the same time, reading the same data, to reduce signal distortion by processing the signal differentially so that any nonlinearities arising from the shape of the MR curve are canceled out.
In a coupled element design, the two elements may be placed atop each other in close proximity. This allows the sensors to provide magnetic bias for each other, as well as providing the benefits of differential sensing. The design has an added benefit of high output, since it is essentially two elements occupying the same space that one would under normal circumstances.
One of the difficulties in making coupled element sensors is that for high linear densities, gap lengths must be made very small, and therefore the films making up the MR sensors must be separated by only a very thin insulator. Furthermore, because of the stacked nature of the design, all interconnection metallization must traverse steps where one material ends, and an insulating material tends to thin down.
Additionally, with narrow track widths and line widths, any misalignment of one element to the other, or misalignment of the interconnection leads to either element, can cause shorting. Finally, in current designs, the head is finished by placing a closure piece on top of the film stack, such that the pressure from bonding of the closure piece can bring on shorts where alignment is marginal.
In the multitrack environment, yield is of a paramount concern, as shorted tracks cannot be simply culled out. Instead, if any one sensor is defective, the entire array must be failed. Therefore, there exist a need for a multitrack coupled element read head design and a method for manufacturing such a read head that eliminates any avenues of shorting or discontinuities.